A powerful explosion ripped through a mosque in southwest Pakistan during Friday evening prayers, killing a senior police officer and at least 11 others, police said.

The bombing also wounded 11 other worshipers in the city of Quetta, the capital of the restive Baluchistan province, said local police chief Mohammad Ajmal.

The slain police officer was the likely target of the attack, but authorities were still investigating, Ajmal said. Both he and hospital officials said the death toll from the bombing could rise as some of the wounded were in critical condition.

No one immediately claimed responsibility for the bombing. But the attack came just days after a roadside bomb in Quetta hit a paramilitary force vehicle, killing two troops.

Hizbul Ahrar, an offshoot of the Pakistani Taliban, claimed responsibility for Tuesday's attack.

Last May, a bombing at a mosque in Quetta killed two people, including the prayer leader, and wounded 28 worshipers. In August, a powerful bomb exploded inside a mosque during Friday prayers on Quena's outskirts.

Although Pakistani militants often carry out such attacks, Baluchistan province is also the scene of a low-level insurgency by separatists demanding more autonomy and a greater share in the region's natural resources such as gas and oil.

The Afghan Taliban have had a strong presence in Quetta. The province shares a long border with Afghanistan and Iran.

Pakistan's government claims it has quelled the insurgency, but violence has continued.